The present invention relates to centrifugally cast hollow straight sided fiberglass reinforced columns used for example as architectural structures as vertical support members and as ornamentation and to the method of casting such columns.
Centrifugally cast fiberglass reinforced columns are typically fabricated by depositing a predetermined amount of uncured fiberglass reinforced plastic (FRP) material in a column mold and then rotating/spinning the mold to cause the uncured FRP material to move outwardly by centrifugal force into engagement with the interior walls of the mold. The mold is continuously rotated until the FRP material has cured sufficiently to permit the column to be removed from the mold.
The exterior shape of the column will generally correspond to the interior contour of the mold. However, the wall thickness of a centrifugally cast FRP multi-sided column is typically not uniform throughout its circumference because of a build up of the FRP material that occurs at the corners of the mold during mold rotation. Accordingly, more FRP material must be used to centrifugally cast a multi-sided column of the desired minimum wall thickness intermediate the corners. Not only does this significantly add to the overall cost of the column, the greater mass of FRP material at the corners results in more shrinkage at the corners during curing causing the sides of the column to become slightly concave instead of straight.
There is thus a need for a centrifugally cast multi-sided FRP column that has straight sides and a substantially uniform wall thickness throughout its circumference. Also there is a need to be able to make such columns at less cost.
The present invention relates to centrifugally cast multi-sided hollow FRP columns that have a substantially uniform wall thickness throughout their periphery and straight sides. Also, the invention relates to a method of centrifugally casting such columns that minimizes the amount of FRP material required to obtain a desired minimum wall thickness throughout the circumference of the columns. This is accomplished by placing angled corner fillers adjacent the corners of the mold with the angled sides of the corner fillers supported in spaced relation from the adjacent wall surfaces of the mold at the mold corners a distance slightly greater than the desired minimum wall thickness of the columns.
The hypotenuse of the corner fillers is desirably outwardly radiused (i.e., convexly curved) to aid in the flow of the FRP material around the corner fillers and into the space between the corner fillers and adjacent wall surfaces of the mold at the mold corners during mold rotation. Also, the radiused hypotenuse of the corner fillers adds to the stiffness/rigidity of the corner fillers, which must be rigid enough to maintain the desired spacing between the corner fillers and adjacent interior walls of the mold at the mold corners.
The corner fillers are extruded out of a suitable plastic material such as high impact polystyrene to which a wood filler may be added to further increase the rigidity of the corner fillers. The ends of the corner fillers are supported in spaced relation from the interior walls of the mold at the corners by spacer inserts placed in the ends of the mold. These spacer inserts may have protrusions thereon shaped for close sliding receipt into the hollow ends of the corner fillers.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter more fully described and particularly pointed out in the claims, the following description and annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but several of the various ways in which the principles of the invention may be employed.